The present invention relates to a modular control device for open-loop control and/or closed-loop control of a technical installation. More particularly, the invention relates to an improved modular design of a backplane for use in such a control device.
A prior art control device is known from the applicant's system description “PSSuniversal, Programmable Control Systems PSS®, System Description No. 21256-EN-04”. PSSuniversal comprises various modules including electronic modules and what is called base modules. The electronic module are designed to be plugged onto the base modules. The base modules are designed to be arranged adjacent to one another in order to form a backplane including a bus line for interconnecting the electronic modules.
There are different types of the electronic modules in this prior art system. In a first type, the electronic module can be an input/output module, i.e. a module that has inputs for connecting sensors and/or has outputs for connecting actuators. In such a case, the electronic module may transmit sensor data via the bus line to a remote programmable logic controller, and/or the electronic module may receive control data from the programmable logic controller via the bus line, said control data being output in the form of control signals to the actuators. In a second type, the electronic module can be a voltage supply module, also termed a power supply module. The voltage supply module is used for establishing what is called Module Supply, i.e. it is used for feeding a supply voltage to other electronic modules, and/or it is used for establishing a Periphery Supply, i.e. for feeding a supply voltage to the sensors and/or actuators. By using a plurality of power supply modules it is possible to build a plurality of separate voltage potential groups, which is advantageous to meet requirements for a high load currents in a flexible manner.
For an input/output module, a specific base module is required that comprises bus connections in two directions (to the right-hand side and to the left-hand side) of the longitudinal direction in order to switch through the data and also the supply voltage from the module that is lying on the left-hand side to the module that is lying on the right-hand side. The corresponding base module is therefore referred to as a base module with a through-connected bus. For a voltage supply module, however, a special base module is required that is not connected to the supply voltage bus in a first direction (e.g. to the left-hand side), but is connected in the opposite direction (e.g. to the right-hand side).
Although this prior art system thus provides some desired flexibility in terms of allowing separate voltage potential groups, a reconfiguration involving a change of the voltage supply requires to change the backplane which can be cumbersome in some situations. Moreover, different types of base modules have to be produced and maintained.